Pneumatic tire

ABSTRACT

Provided is a pneumatic tire having sufficient sealing performance. The present invention relates to a pneumatic tire including a sealant layer located radially inside an innerliner, the sealant layer being formed by applying a sealant to the inner periphery of a tire from which mold release agents have been removed.

TECHNICAL FIELD

The present invention relates to a pneumatic tire.

BACKGROUND ART

Self-sealing tires with sealants applied to the inner peripheriesthereof have been known as puncture resistant pneumatic tires(hereinafter, pneumatic tires are also referred to simply as tires).Sealants automatically seal puncture holes formed in such self-sealingtires.

Several methods have been known for producing self-sealing tires,including, for example, a method that includes: adding an organicsolvent to a sealant to reduce the viscosity of the sealant so as to beeasy to handle; attaching the diluted sealant to the inner surface of atire; and removing the organic solvent from the attached dilutedsealant, and a method that includes: mixing a base agent prepared in abatch kneader with a curing agent using a static mixer or dynamic mixerto prepare a sealant; and attaching the sealant to the inner peripheryof a tire (see, for example, Patent Literature 1).

Patent Literature 2 discloses a method including attaching a sealant toan unvulcanized innerliner on an assembly drum, i.e., attaching asealant to the inner periphery of an unvulcanized tire.

Patent Literature 3 discloses a method including pressure-bonding asealant to a sponge layer and attaching the sponge layer to the innerperiphery of a tire.

Patent Literature 4 discloses a method including attaching a sealant tothe inner periphery of a tire by pressing with a pressure roller.

CITATION LIST Patent Literature

Patent Literature 1: JP 2010-528131 T

Patent Literature 2: JP 2008-149714 A

Patent Literature 3: JP 2002-347418 A

Patent Literature 4: JP 2001-18609 A

SUMMARY OF INVENTION Technical Problem

However, since the sealants have a certain level of viscosity so as tobe prevented from flowing, they may show insufficient adhesion. For thisreason, the sealants are difficult to attach to the inner peripheries oftires in some cases. As a result of extensive studies, the presentinventors have found that mold release agents are usually applied to theinner peripheries of tires to avoid adhesion between the bladder and thetire during vulcanization, and unfortunately the presence of such moldrelease agents may hinder successful application of sealants to thetires during the sealant application or may cause dislocation orseparation of the sealants during service, thereby resulting invibration or insufficient sealing performance.

The present invention aims to solve the problems and provide a pneumatictire (self-sealing tire) having sufficient sealing performance.

Solution To Problem

The present inventors made further extensive studies and have found thatby applying a sealant to the inner periphery of a tire from which moldrelease agents have been removed, the adhesion between the sealant andthe inner periphery of the tire is improved, and therefore the sealantcan be successfully applied to the inner periphery of the tire in thesealant application, and does not dislocate or separate during service,thereby causing no vibration but providing sufficient sealingperformance.

Specifically, the present invention relates a pneumatic tire(self-sealing tire), including a sealant layer located radially insidean innerliner, the sealant layer being formed by applying a sealant toan inner periphery of a tire from which mold release agents have beenremoved.

Preferably, the sealant layer is formed by continuously and spirallyapplying a generally string-shaped sealant to an inner periphery of atire from which mold release agents have been removed, in a tire widthdirection from one side to the other.

A surface of the inner periphery of a tire is preferably scraped.

The sealant is preferably applied to an entire area of the innerperiphery of a tire from which mold release agents have been removed.

Preferably, a length of the sealant layer in a tire width direction anda length in the tire width direction of the area of the inner peripheryof a tire from which mold release agents have been removed satisfy thefollowing formula:

0 mm<(the length of the sealant layer in a tire width direction)−(thelength in the tire width direction of the area from which mold releaseagents have been removed)≦16.0 mm.

Preferably, a length in a tire width direction of an area of the sealantlayer formed by applying a sealant to an inner periphery of a tire fromwhich mold release agents have been removed and a length of a breaker ofthe tire in the tire width direction satisfy the following formula:

0 mm≦(the length in a tire width direction of an area of the sealantlayer formed by applying a sealant to an inner periphery of a tire fromwhich mold release agents have been removed)−(the length of a breaker inthe tire width direction)≦8.0 mm.

Preferably, an attachment start portion of the sealant is locatedtire-widthwise inward from a tire-widthwise end of the sealant layer.

Preferably, the sealant layer is formed by continuously applying agenerally string-shaped sealant to an inner periphery of a tire from theattachment start portion toward the tire-widthwise end of the sealantlayer, and then

-   -   continuously and spirally applying a generally string-shaped        sealant to the inner periphery of a tire from the tire-widthwise        end of the sealant layer toward the other tire-widthwise end of        the sealant layer.

Preferably, an application position assumed when the sealant is appliedfrom the attachment start portion toward the tire-widthwise end of thesealant layer is moved in a tire width direction at a higher velocitythan an application position assumed when the sealant is applied fromthe tire-widthwise end of the sealant layer toward the othertire-widthwise end of the sealant layer.

Preferably, the attachment start portion is located within an area ofthe inner periphery of a tire from which mold release agents have beenremoved.

Preferably, the sealant contains a rubber component including abutyl-based rubber, a liquid polymer, and an organic peroxide, and thesealant contains 1 to 30 parts by mass of an inorganic filler relativeto 100 parts by mass of the rubber component.

The sealant layer preferably has a thickness of 1.0 to 10.0 mm.

The sealant layer preferably has a width that is 85% to 115% of that ofa breaker of the tire.

Preferably, the sealant layer is formed by sequentially preparing asealant by mixing raw materials including a crosslinking agent using acontinuous kneader, and sequentially applying the sealant to an innerperiphery of a tire.

Preferably, the sealant discharged from an outlet of the continuouskneader has a temperature of 70° C. to 150° C.

Advantageous Effects of Invention

The pneumatic tire (self-sealing tire) of the present invention is aself-sealing tire including a sealant layer located radially inside aninnerliner. The sealant layer is formed by applying a sealant to theinner periphery of a tire from which mold release agents have beenremoved. Such a pneumatic tire has sufficient sealing performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view schematically showing an example of anapplicator used in a method for producing a self-sealing tire.

FIG. 2 is an enlarged view showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1.

FIG. 3 is an explanatory view schematically showing the positionalrelationship of the nozzle to the tire.

FIG. 4 is an explanatory view schematically showing an example of agenerally string-shaped sealant continuously and spirally attached tothe inner periphery of a tire.

FIG. 5 are enlarged views showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1.

FIG. 6 is an explanatory view schematically showing an example of asealant attached to a self-sealing tire.

FIG. 7 is an explanatory view schematically showing an example of aproduction facility used in a method for producing a self-sealing tire.

FIG. 8 is an explanatory view schematically showing an example of across section of the sealant shown in FIG. 4 when the sealant is cutalong the straight line A-A orthogonal to the direction along which thesealant is applied (longitudinal direction).

FIG. 9 is an explanatory view schematically showing an example of across section of a pneumatic tire.

FIGS. 10(a) to 10(d) are explanatory views each schematically showing anexample of a generally string-shaped sealant continuously and spirallyattached to the inner periphery of a tire.

DESCRIPTION OF EMBODIMENTS

The pneumatic tire (self-sealing tire) of the present invention is aself-sealing tire including a sealant layer located radially inside aninnerliner, and the sealant layer is formed by applying a sealant to theinner periphery of a tire from which mold release agents have beenremoved.

According to the present invention, since a sealant layer is formed byapplying a sealant to the inner periphery of a tire from which moldrelease agents have been removed, the adhesion between the sealant andthe inner periphery of the tire is improved, and therefore the sealantcan be successfully applied to the inner periphery of the tire in thesealant application, and further the sealant does not dislocate orseparate during service, thereby causing no vibration but providingsufficient sealing performance, especially at the tire-widthwise end ofa breaker which is the longest in the width direction of the tire.

The sealant layer in the present invention is preferably formed bycontinuously and spirally applying a generally string-shaped sealant tothe inner periphery of a tire from which mold release agents have beenremoved, in the tire width direction from one side to the other. Thisallows for stable production of self-sealing tires having much bettersealing performance with high productivity.

An innerliner, which is a rubber component forming the inner peripheryof a tire, is made from a rubber having a low air permeability. It is atire component provided to ensure air retention properties for tires.When mold release agents have been removed from the tire innerperiphery, e.g. as described later, the tire inner periphery from whichmold release agents have been removed has a scraped surface. Thus, theinnerliner layer is made thinner and may not ensure sufficient airretention properties due to air leakage from this part.

Since sealants also have low air permeability, if a sealant is appliedto the thinner part of the innerliner layer resulting from the removalof mold release agents, the sealant can compensate for the loss of airretention properties, thereby ensuring air retention properties for thetire. For this reason, in the present invention, a sealant is preferablyapplied to the entire area of the inner periphery of a tire from whichmold release agents have been removed. In this case, the sealant cansupplement air retention properties and allow even the thinnerinnerliner layer to ensure sufficient air retention properties.Furthermore, by controlling the length of the sealant layer in the tirewidth direction and the length in the tire width direction of the areaof the inner periphery of the tire from which mold release agents havebeen removed, as described later, the self-sealing tire can have abetter balance of sealing performance and air retention properties.

The self-sealing tire of the present invention is preferably aself-sealing tire including a sealant layer located radially inside aninnerliner, wherein the sealant layer is formed by continuously andspirally applying a generally string-shaped sealant to the innerperiphery of a tire in the tire width direction from one side to theother, and the attachment start portion of the sealant is locatedtire-widthwise inward from the tire-widthwise end of the sealant layer.

When a sealant layer is formed by continuously and spirally applying agenerally string-shaped sealant to the inner periphery of a tire in thetire width direction from one side to the other, the attachment startportion of the sealant is ideally and desirably attached as shown inFIG. 10(a).

However, since the generally string-shaped sealant has a certain levelof viscosity so as to be prevented from flowing, unfortunately thesealant may show insufficient adhesion and can easily peel offespecially at the attachment start portion. Due to this, the attachmentstart portion may separate from the surface and bend outwardly in thetire width direction as shown in FIG. 10(b), or may separate from thesurface and entangled with the following portion as shown in FIG. 10(c).In the case of the sealant layer as shown in FIG. 10(b) or 10(c), it mayfail to exhibit sufficient sealing performance for puncture holes formedin the shaded areas. Thus, sufficient sealing performance may not beobtained over the entire area where the sealant is attached.

In the self-sealing tire of the present invention, the sealantattachment start portion is preferably located tire-widthwise inwardfrom the tire-widthwise end of the sealant layer as shown in FIG. 10(d).In this case, the entire sealant layer can have sufficient sealingperformance even when the attachment start portion of the sealant ispeeled. More specifically, in the self-sealing tire of the presentinvention, the sealant layer is preferably formed by continuouslyapplying a generally string-shaped sealant to the inner periphery of atire from the attachment start portion located tire-widthwise inwardfrom the tire-widthwise end of the sealant layer toward thetire-widthwise end of the sealant layer, and then continuously andspirally applying a generally string-shaped sealant to the innerperiphery of the tire from the tire-widthwise end of the sealant layertoward the other tire-widthwise end of the sealant layer. In this case,the sealant is additionally applied to the attachment start portion byapplying the sealant from one tire-widthwise end of the sealant layertoward the other tire-widthwise end of the sealant layer. As a result,the entire sealant layer can have sufficient sealing performance evenwhen the attachment start portion of the sealant is poorly applied.

Particularly when the sealant used is a sealant having a composition asdescribed later, more suitable effects can be obtained. Furthermore, thesealant having the later-described composition automatically sealspuncture holes even in a low temperature environment.

When the sealant having the later-described composition is prepared byusing an organic peroxide as a crosslinking agent or incorporating arubber component including a butyl-based rubber with a liquid polymersuch as liquid polybutene, especially wherein the liquid polymer is acombination of two or more materials having different viscosities, thesealant can achieve a balanced improvement in adhesion, sealingperformance, fluidity, and processability. This is probably because theintroduction of a liquid polymer component to an organic peroxidecrosslinking system using butyl rubber as the rubber component providesadhesion, and especially the use of liquid polymers having differentviscosities reduces flowing of the sealant during high-speed running (athigh temperatures); therefore, the sealant can achieve a balancedimprovement in the above properties. Furthermore, the incorporation of 1to 30 parts by mass of an inorganic filler relative to 100 parts by massof the rubber component allows the sealant to achieve a more balancedimprovement in adhesion, sealing performance, fluidity, andprocessability.

The following describes suitable examples of the method for producing aself-sealing tire of the present invention.

A self-sealing tire can be produced, for example, by preparing a sealantby mixing the components of the sealant, and then attaching the sealantto the inner periphery of a tire by application or other means to form asealant layer. The self-sealing tire includes the sealant layer locatedradially inside an innerliner.

The hardness (viscosity) of the sealant needs to be adjusted to anappropriate viscosity according to the service temperature bycontrolling the rubber component and the degree of crosslinking. Therubber component is controlled by varying the type and amount of liquidrubber, plasticizers, or carbon black, while the degree of crosslinkingis controlled by varying the type and amount of crosslinking agents orcrosslinking activators.

Any sealant that shows adhesion may be used, and rubber compositionsconventionally used to seal punctures of tires can be used. The rubbercomponent constituting a main ingredient of such a rubber compositionmay include a butyl-based rubber. Examples of the butyl-based rubberinclude butyl rubber (IIR) and halogenated butyl rubbers (X-IIR) such asbrominated butyl rubber (Br-IIR) and chlorinated butyl rubber (Cl-IIR).In particular, in view of fluidity and other properties, either or bothof butyl rubber and halogenated butyl rubbers can be suitably used. Thebutyl-based rubber to be used is preferably in the form of pellets. Sucha pelletized butyl-based rubber can be precisely and suitably suppliedto a continuous kneader so that the sealant can be produced with highproductivity.

To reduce the deterioration of the fluidity of the sealant, thebutyl-based rubber to be used is preferably a butyl-based rubber Ahaving a Mooney viscosity M₁₊₈ at 125° C. of at least 20 but less than40 and/or a butyl-based rubber B having a Mooney viscosity ML₁₊₈ at 125°C. of at least 40 but not more than 80. It is particularly suitable touse at least the butyl-based rubber A. When the butyl-based rubbers Aand B are used in combination, the blending ratio may be appropriatelychosen.

The Mooney viscosity M₁₊₈ at 125° C. of the butyl-based rubber A is morepreferably 25 or more, still more preferably 28 or more, but morepreferably 38 or less, still more preferably 35 or less. If the Mooneyviscosity is less than 20, the fluidity may be reduced. If the Mooneyviscosity is 40 or more, the effect of the combined use may not beachieved.

The Mooney viscosity ML₁₊₈ at 125° C. of the butyl-based rubber B ismore preferably 45 or more, still more preferably 48 or more, but morepreferably 70 or less, still more preferably 60 or less. If the Mooneyviscosity is less than 40, the effect of the combined use may not beachieved. If the Mooney viscosity is more than 80, sealing performancemay be reduced.

The Mooney viscosity ML₁₊₈ at 125° C. is determined in conformity withJIS K-6300-1:2001 at a test temperature of 125° C. using an L type rotorwith a preheating time of one minute and a rotation time of eightminutes.

The rubber component may be a combination with other ingredients such asdiene rubbers, including natural rubber (NR), polyisoprene rubber (IR),polybutadiene rubber (BR), styrene-butadiene rubber (SBR),styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-dienerubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber(NBR), and butyl rubber (IIR). In view of fluidity and other properties,the amount of the butyl-based rubber based on 100% by mass of the rubbercomponent is preferably 90% by mass or more, more preferably 95% by massor more, particularly preferably 100% by mass.

Examples of the liquid polymer used in the sealant include liquidpolybutene, liquid polyisobutene, liquid polyisoprene, liquidpolybutadiene, liquid poly-α-olefin, liquid isobutylene, liquidethylene-α-olefin copolymers, liquid ethylene-propylene copolymers, andliquid ethylene-butylene copolymers. To provide adhesion and otherproperties, liquid polybutene is preferred among these. Examples of theliquid polybutene include copolymers having a long-chain hydrocarbonmolecular structure which is based on isobutene and further reacted withnormal butene. Hydrogenated liquid polybutene may also be used.

To prevent the sealant from flowing during high-speed running, theliquid polymer (e.g. liquid polybutene) to be used is preferably aliquid polymer A having a kinematic viscosity at 100° C. of 550 to 625mm²/s and/or a liquid polymer B having a kinematic viscosity at 100° C.of 3,540 to 4,010 mm²/s, more preferably a combination of the liquidpolymers A and B.

The kinematic viscosity at 100° C. of the liquid polymer

A (e.g. liquid polybutene) is preferably 550 mm²/s or higher, morepreferably 570 mm²/s or higher. If the kinematic viscosity is lower than550 mm²/s, flowing of the sealant may occur. The kinematic viscosity at100° C. is preferably 625 mm²/s or lower, more preferably 610 mm²/s orlower. If the kinematic viscosity is higher than 625 mm²/s, the sealantmay have higher viscosity and deteriorated extrudability.

The kinematic viscosity at 100° C. of the liquid polymer B (e.g. liquidpolybutene) is preferably 3,600 mm²/s or higher, more preferably 3,650mm²/s or higher. If the kinematic viscosity is lower than 3,540 mm²/s,the sealant may have too low a viscosity and easily flow during serviceof the tire, resulting in deterioration of sealing performance oruniformity.

The kinematic viscosity at 100° C. is preferably 3, 900 mm²/s or lower,more preferably 3,800 mm²/s or lower. If the kinematic viscosity ishigher than 4,010 mm²/s, sealing performance may deteriorate.

The kinematic viscosity at 40° C. of the liquid polymer A (e.g. liquidpolybutene) is preferably 20,000 mm²/s or higher, more preferably 23,000mm²/s or higher. If the kinematic viscosity is lower than 20,000 mm²/s,the sealant may be soft so that its flowing can occur. The kinematicviscosity at 40° C. is preferably 30,000 mm²/s or lower, more preferably28,000 mm²/s or lower. If the kinematic viscosity is higher than 30,000mm²/s, the sealant may have too high a viscosity and deterioratedsealing performance.

The kinematic viscosity at 40° C. of the liquid polymer B (e.g. liquidpolybutene) is preferably 120,000 mm²/s or higher, more preferably150,000 mm²/s or higher. If the kinematic viscosity is lower than120,000 mm²/s, the sealant may have too low a viscosity and easily flowduring service of the tire, resulting in deterioration of sealingperformance or uniformity.

The kinematic viscosity at 40° C. is preferably 200,000 mm²/s or lower,more preferably 170,000 mm²/s or lower. If the kinematic viscosity ishigher than 200,000 mm²/s, the sealant may have too high a viscosity anddeteriorated sealing performance.

The kinematic viscosity is determined in conformity with JIS K 2283-2000at 100° C. or 40° C.

The amount of the liquid polymer (the combined amount of the liquidpolymers A and B and other liquid polymers) relative to 100 parts bymass of the rubber component is preferably 50 parts by mass or more,more preferably 100 parts by mass or more, still more preferably 150parts by mass or more. If the amount is less than 50 parts by mass,adhesion may be reduced. The amount is preferably 400 parts by mass orless, more preferably 300 parts by mass or less, still more preferably250 parts by mass or less. If the amount is more than 400 parts by mass,flowing of the sealant may occur.

In the case where the liquid polymers A and B are used in combination,the blending ratio of these polymers [ (amount of liquid polymerA)/(amount of liquid polymer B) ] is preferably 10/90 to 90/10, morepreferably 30/70 to 70/30, still more preferably 40/60 to 60/40. Whenthe blending ratio is within the range indicated above, the sealant isprovided with good adhesion.

The organic peroxide (crosslinking agent) is not particularly limited,and conventionally known compounds can be used. The use of a butyl-basedrubber and a liquid polymer in an organic peroxide crosslinking systemimproves adhesion, sealing performance, fluidity, and processability.

Examples of the organic peroxide include acyl peroxides such as benzoylperoxide, dibenzoyl peroxide, and p-chlorobenzoyl peroxide; peroxyesterssuch as 1-butyl peroxyacetate, t-butyl peroxybenzoate, and t-butylperoxyphthalate; ketone peroxides such as methyl ethyl ketone peroxide;alkyl peroxides such as di-t-butyl peroxybenzoate and 1,3-bis(1-butylperoxyisopropyl) benzene; hydroperoxides such as t-butylhydroperoxide; and dicumyl peroxide and t-butylcumyl peroxide. In viewof adhesion and fluidity, acyl peroxides are preferred among these, withdibenzoyl peroxide being particularly preferred. Moreover, the organicperoxide (crosslinking agent) to be used is preferably in the form ofpowder. Such a powdered organic peroxide (crosslinking agent) can beprecisely and suitably supplied to a continuous kneader so that thesealant can be produced with high productivity.

The amount of the organic peroxide (crosslinking agent) relative to 100parts by mass of the rubber component is preferably 0.5 parts by mass ormore, more preferably 1 part by mass or more, still more preferably 5parts by mass or more. If the amount is less than 0.5 parts by mass,crosslink density may decrease so that flowing of the sealant can occur.The amount is preferably 40 parts by mass or less, more preferably 20parts by mass or less, still more preferably 15 parts by mass or less.If the amount is more than 40 parts by mass, crosslink density mayincrease so that the sealant can be hardened and show reduced sealingperformance.

The crosslinking activator (vulcanization accelerator) to be used may beat least one selected from the group consisting of sulfenamidecrosslinking activators, thiazole crosslinking activators, thiuramcrosslinking activators, thiourea crosslinking activators, guanidinecrosslinking activators, dithiocarbamate crosslinking activators,aldehyde-amine crosslinking activators, aldehyde-ammonia crosslinkingactivators, imidazoline crosslinking activators, xanthate crosslinkingactivators, and quinone dioxime compounds (quinoid compounds). Forexample, quinone dioxime compounds (quinoid compounds) can be suitablyused. The use of a butyl-based rubber and a liquid polymer in acrosslinking system including a crosslinking activator added to anorganic peroxide improves adhesion, sealing performance, fluidity, andprocessability.

Examples of the quinone dioxime compound include p-benzoquinone dioxime,p-quinone dioxime, p-quinone dioxime diacetate, p-quinone dioximedicaproate, p-quinone dioxime dilaurate, p-quinone dioxime distearate,p-quinone dioxime dicrotonate, p-quinone dioxime dinaphthenate,p-quinone dioxime succinate, p-quinone dioxime adipate, p-quinonedioxime difuroate, p-quinone dioxime dibenzoate, p-quinone dioximedi(o-chlorobenzoate), p-quinone dioxime di(p-chlorobenzoate), p-quinonedioxime di(p-nitrobenzoate), p-quinone dioxime di(m-nitrobenzoate),p-quinone dioxime di(3,5-dinitrobenzoate), p-quinone dioximedi(p-methoxybenzoate) p-quinone dioxime di(n-amyloxybenzoate), andp-quinone dioxime di(m-bromobenzoate). In view of adhesion, sealingperformance, and fluidity, p-benzoquinone dioxime is preferred amongthese. Moreover, the crosslinking activator (vulcanization accelerator)to be used is preferably in the form of powder. Such a powderedcrosslinking activator (vulcanization accelerator) can be precisely andsuitably supplied to a continuous kneader so that the sealant can beproduced with high productivity.

The amount of the crosslinking activator (e.g. quinone dioximecompounds) relative to 100 parts by mass of the rubber component ispreferably 0.5 parts by mass or more, more preferably 1 part by mass ormore, still more preferably 3 parts by mass or more. If the amount isless than 0.5 parts by mass, flowing of the sealant may occur. Theamount is preferably 40 parts by mass or less, more preferably 20 partsby mass or less, still more preferably 15 parts by mass or less. If theamount is more than 40 parts by mass, sealing performance may bereduced.

The sealant may further contain an inorganic filler such as carbonblack, silica, calcium carbonate, calcium silicate, magnesium oxide,aluminum oxide, barium sulfate, talc, or mica; or a plasticizer such asaromatic process oils, naphthenic process oils, or paraffinic processoils.

The amount of the inorganic filler relative to 100 parts by mass of therubber component is preferably 1 part by mass or more, more preferably10 parts by mass or more. If the amount is less than 1 part by mass,sealing performance may be reduced due to degradation by ultravioletrays. The amount is preferably 50 parts by mass or less, more preferably40 parts by mass or less, still more preferably 30 parts by mass orless. If the amount is more than 50 parts by mass, the sealant may havetoo high a viscosity and deteriorated sealing performance.

To prevent degradation by ultraviolet rays, the inorganic filler ispreferably carbon black. In this case, the amount of the carbon blackrelative to 100 parts by mass of the rubber component is preferably 1part by mass or more, more preferably 10 parts by mass or more. If theamount is less than 1 part by mass, sealing performance may be reduceddue to degradation by ultraviolet rays. The amount is preferably 50parts by mass or less, more preferably 40 parts by mass or less, stillmore preferably 25 parts by mass or less. If the amount is more than 50parts by mass, the sealant may have too high a viscosity anddeteriorated sealing performance.

The amount of the plasticizer relative to 100 parts by mass of therubber component is preferably 1 part by mass or more, more preferably 5parts by mass or more. If the amount is less than 1 part by mass, thesealant may show lower adhesion to tires, failing to provide sufficientsealing performance. The amount is preferably 40 parts by mass or less,more preferably 20 parts by mass or less. If the amount is more than 40parts by mass, the sealant may slide in the kneader so that it cannot beeasily kneaded.

The sealant is preferably prepared by mixing a pelletized butyl-basedrubber, a powdered crosslinking agent, and a powdered crosslinkingactivator, and more preferably by mixing a pelletized butyl-basedrubber, a liquid polybutene, a plasticizer, carbon black powder, apowdered crosslinking agent, and a powdered crosslinking activator. Suchraw materials can be suitably supplied to a continuous kneader so thatthe sealant can be produced with high productivity.

The sealant is preferably obtained by incorporating a rubber componentincluding butyl rubber with predetermined amounts of a liquid polymer,an organic peroxide, and a crosslinking activator.

A sealant obtained by incorporating butyl rubber with a liquid polymersuch as liquid polybutene, especially wherein the butyl rubber and theliquid polymer are each a combination of two or more materials havingdifferent viscosities, can achieve a balanced improvement in adhesion,sealing performance, fluidity, and processability. This is because theintroduction of a liquid polymer component to an organic peroxidecrosslinking system using butyl rubber as the rubber component providesadhesion, and especially the use of liquid polymers or solid butylrubbers having different viscosities reduces flowing of the sealantduring high-speed running. Therefore, the sealant can achieve abalanced, improvement in adhesion, sealing performance, fluidity, andprocessability.

The viscosity at 40° C. of the sealant is not particularly limited. Inorder to allow the sealant to suitably maintain a generally string shapewhen it is applied to the inner periphery of a tire, and in view ofadhesion, fluidity, and other properties, the viscosity at 40° C. ispreferably 3,000 Pa·s or higher, more preferably 5,000 Pa·s or higher,but preferably 70,000 Pa·s or lower, more preferably 50,000 Pa·s orlower. If the viscosity is lower than 3,000 Pa·s, the applied sealantmay flow when the tire stops rotating, so that the sealant cannotmaintain the film thickness. Also, if the viscosity is higher than70,000 Pa·s, the sealant cannot be easily discharged from the nozzle.

The viscosity of the sealant is determined at 40° C. in conformity withJIS K 6833 using a rotational viscometer.

A self-sealing tire including a sealant layer located radially inside aninnerliner can be produced by preparing a sealant by mixing theaforementioned materials, and applying the sealant to the innerperiphery of a tire, and preferably to the radially inner side of aninnerliner. The materials of the sealant may be mixed using knowncontinuous kneaders, for example. In particular, they are preferablymixed using a co-rotating or counter-rotating multi-screw kneadingextruder and particularly using a twin screw kneading extruder.

The continuous kneader (especially twin screw kneading extruder)preferably has a plurality of supply ports for supplying raw materials,more preferably at least three supply ports, still more preferably atleast three supply ports including upstream, midstream, and downstreamsupply ports. By sequentially supplying the raw materials to thecontinuous kneader (especially twin screw kneading extruder), the rawmaterials are mixed and sequentially and continuously prepared into asealant.

Preferably, the raw materials are sequentially supplied to thecontinuous kneader (especially twin screw kneading extruder), startingfrom the material having a higher viscosity. In this case, the materialscan be sufficiently mixed and prepared into a sealant of a consistentquality. Moreover, powder materials, which improve kneadability, shouldbe introduced as upstream as possible.

The organic peroxide is preferably supplied to the continuous kneader(especially twin screw kneading extruder) through its downstream supplyport. In this case, the time period from supplying the organic peroxideto applying the sealant to a tire can be shortened so that the sealantcan be applied to a tire before it is cured. This allows for more stableproduction of self-sealing tires.

Since kneading is unsuccessfully accomplished when a large amount of theliquid polymer is introduced at once into the continuous kneader(especially twin screw kneading extruder), the liquid polymer ispreferably supplied to the continuous kneader (especially twin screwkneading extruder) through a plurality of supply ports. In this case,the sealant can be more suitably kneaded.

When a continuous kneader (especially twin screw kneading extruder) isused, the sealant is preferably prepared using the continuous kneader(especially twin screw kneading extruder) having at least three supplyports by supplying a rubber component such as a butyl-based rubber, aninorganic filler, and a crosslinking activator each from the upstreamsupply port, a liquid polymer B from the midstream supply port, and aliquid polymer A, an organic peroxide, and a plasticizer each from thedownstream supply port of the continuous kneader (especially twin screwkneading extruder), followed by kneading and extrusion. The materialssuch as liquid polymers may be entirely or partially supplied from therespective supply ports. Preferably, 95% by mass or more of the totalamount of each material is supplied from the supply port.

Preferably, all the raw materials to be introduced into the continuouskneader are introduced into the continuous kneader under the control ofa quantitative feeder. This allows for continuous and automatedpreparation of the sealant.

Any feeder that can provide quantitative feeding may be used, includingknown feeders such as screw feeders, plunger pumps, gear pumps, andmohno pumps.

Solid raw materials (especially pellets or powder) such as pelletizedbutyl-based rubbers, carbon black powder, powdered crosslinking agents,and powdered crosslinking activators are preferably quantitativelysupplied using a screw feeder. This allows the solid raw materials to besupplied precisely in fixed amounts, thereby allowing for the productionof a higher quality sealant and therefore a higher quality self-sealingtire.

Moreover, the solid raw materials are preferably individually suppliedthrough separate respective feeders. In this case, the raw materialsneed not to be blended beforehand, which facilitates supply of thematerials in the mass production.

The plasticizer is preferably quantitatively supplied using a plungerpump. This allows the plasticizer to be supplied precisely in a fixedamount, thereby allowing for the production of a higher quality sealantand therefore a higher quality self-sealing tire.

The liquid polymer is preferably quantitatively supplied using a gearpump. This allows the liquid Polymer to be supplied precisely in a fixedamount, thereby allowing for the production of a higher quality sealantand therefore a higher quality self-sealing tire.

The liquid polymer to be supplied is preferably kept under constanttemperature control. The constant temperature control allows the liquidpolymer to be supplied more precisely in a fixed amount. The liquidpolymer to be supplied preferably has a temperature of 20° C. to 90° C.,more preferably 40° C. to 70° C.

In view of easy mixing and extrudability, the mixing in the continuouskneader (especially twin screw kneading extruder) is preferably carriedout at a barrel temperature of 30° C. (preferably 50° C.) to 150° C.

In view of sufficient mixing, preferably, the materials suppliedupstream are mixed for 1 to 3 minutes, and the materials suppliedmidstream are mixed for 1 to 3 minutes, while the materials supplieddownstream are preferably mixed for 0.5 to 2 minutes in order to avoidcrosslinking. The times for mixing the materials each refer to theresidence time in the continuous kneader (especially twin screw kneadingextruder) from supply to discharge. For example, the time for mixing thematerials supplied downstream means the residence time from when theyare supplied through a downstream supply port until they are discharged.

By varying the screw rotational speed of the continuous kneader(especially twin screw kneading extruder) or the setting of atemperature controller, it is possible to control the temperature of thesealant discharged from the outlet and therefore the rate of curingacceleration of the sealant. As the screw rotational speed of thecontinuous kneader (especially twin screw kneading extruder) increases,kneadability and material temperature increase. The screw rotationalspeed does not affect the discharge amount. In view of sufficient mixingand control of the rate of curing acceleration, the screw rotationalspeed is preferably 50 to 700 (preferably 550) rpm.

In view of sufficient mixing and control of the rate of curingacceleration, the temperature of the sealant discharged from the outletof the continuous kneader (especially twin screw kneading extruder) ispreferably 70° C. to 150° C., more preferably 90° C. to 130° C. When thetemperature of the sealant is within the range indicated above, thecrosslinking reaction begins upon the application of the sealant and thesealant adheres well to the inner periphery of a tire and, at the sametime, the crosslinking reaction more suitably proceeds, whereby aself-sealing tire having high sealing performance can be produced.Moreover, the crosslinking step described later is not required in thiscase.

The amount of the sealant discharged from the outlet of the continuouskneader (especially twin screw kneading extruder) is determinedaccording to the amounts of the raw materials supplied through thesupply ports. The amounts of the raw materials supplied through thesupply ports are not particularly limited, and a person skilled in theart can appropriately select the amounts. To suitably produce aself-sealing tire having much better uniformity and sealing performance,preferably a substantially constant amount (discharge amount) of thesealant is discharged from the outlet.

Herein, the substantially constant discharge amount means that thedischarge amount varies within a range of 93% to 107%, preferably 97% to103%, more preferably 98% to 102%, still more preferably 99% to 101%.

The outlet of the continuous kneader (especially twin screw kneadingextruder) is preferably connected to a nozzle. Since the continuouskneader (especially twin screw kneading extruder) can discharge thematerials at a high pressure, the prepared sealant can be attached in athin, generally string shape (bead shape) to a tire by means of a nozzle(preferably a small diameter nozzle creating high resistance) mounted onthe outlet. Specifically, by discharging the sealant from a nozzleconnected to the outlet of the continuous kneader (especially twin screwkneading extruder) to sequentially apply it to the inner periphery of atire, the applied sealant has a substantially constant thickness,thereby preventing deterioration of tire uniformity. This allows for theproduction of a self-sealing tire that is excellent in weight balance.

Next, for example, the mixed sealant is discharged from the nozzleconnected to the outlet of the extruder such as a continuous kneader(especially twin screw kneading extruder) to feed and apply the sealantdirectly to the inner periphery of a vulcanized tire, whereby aself-sealing tire can be produced. In this case, since the sealant whichhas been mixed in, for example, a twin screw kneading extruder and inwhich the crosslinking reaction in the extruder is suppressed isdirectly applied to the tire inner periphery, the crosslinking reactionof the sealant begins upon the application and the sealant adheres wellto the tire inner periphery and, at the same time, the crosslinkingreaction suitably proceeds. For this reason, the sealant applied to thetire inner periphery forms a sealant layer while suitably maintaining agenerally string shape. Accordingly, the sealant can be applied andprocessed in a series of steps and therefore productivity is furtherimproved. Moreover, the application of the sealant to the innerperiphery of a vulcanized tire further enhances the productivity ofself-sealing tires. Furthermore, the sealant discharged from the nozzleconnected to the outlet of the continuous kneader (especially twin screwkneading extruder) is preferably sequentially applied directly to thetire inner periphery. In this case, since the sealant in which thecrosslinking reaction in the continuous kneader (especially twin screwkneading extruder) is suppressed is directly and continuously applied tothe tire inner periphery, the crosslinking reaction of the sealantbegins upon the application and the sealant adheres well to the tireinner periphery and, at the same time, the crosslinking reactionsuitably proceeds, whereby a self-sealing tire that is excellent inweight balance can be produced with higher productivity.

With regard to the application of the sealant to the tire innerperiphery, the sealant may be applied at least to the inner periphery ofa tire that corresponds to a tread portion, and more preferably at leastto the inner periphery of a tire that corresponds to a breaker. Omittingthe application of the sealant to areas where the sealant is unnecessaryfurther enhances the productivity of self-sealing tires.

The inner periphery of a tire that corresponds to a tread portion refersto a portion of the inner periphery of a tire that is located radiallyinside a tread portion which contacts the road surface. The innerperiphery of a tire that corresponds to a breaker refers to a portion ofthe inner periphery of a tire that is located radially inside a breaker.

The breaker refers to a component placed inside a tread and radiallyoutside a carcass. Specifically, it is a component shown as a breaker 16in FIG. 9, for example.

Unvulcanized tires are usually vulcanized using bladders. During thevulcanization, such a bladder inflates and closely attaches to the innerperiphery (innerliner) of the tire. Hence, a mold release agent isusually applied to the inner periphery (innerliner) of the tire to avoidadhesion between the bladder and the inner periphery (innerliner) of thetire after completion of the vulcanization.

The mold release agent is usually a water-soluble paint or amold-releasing rubber. However, the presence of the mold release agenton the inner periphery of the tire may impair the adhesion between thesealant and the inner periphery of the tire. For this reason, thepresent invention includes preliminarily removing mold release agentsfrom the tire inner periphery. In particular, it is preferred topreliminarily remove mold release agents at least from a portion of thetire inner periphery in which application of the sealant starts. Thestudies of the present inventors have further revealed that in the caseof a generally string-shaped sealant, unfortunately the sealant is insome cases difficult to attach to the inner periphery of a tire and caneasily peel off especially at the attachment start portion. However, ifthe attachment start portion of the sealant is located within the areaof the tire inner periphery from which mold release agents have beenremoved, the adhesion between the tire inner periphery and the sealantis improved, and therefore the sealant can be successfully applied tothe tire inner periphery in the sealant application. Thus, the aboveproblem is less likely to occur.

It is more preferred to preliminarily remove mold release agents fromthe entire area of the tire inner periphery where the sealant is to beapplied. In this case, the sealant can adhere better to the tire innerperiphery, thereby allowing for the production of a self-sealing tirehaving higher sealing performance.

The removal of mold release agents from the tire inner periphery may becarried out by any method, including known methods such as buffingtreatment, laser treatment, high pressure water washing, and removalwith detergents and preferably with neutral detergents. For example, themold release agents may be washed off with, e.g. water, a surfactant, oran organic solvent while rubbing with, e.g. a brush or cloth, or may bewiped off with, e.g. cloth or paper. Other techniques such as physicallyscraping the surface are also effective. The buffing treatment may becarried out using an apparatus as described in, for example, JP 4866077B. Preferably, the surface of the tire inner periphery is scraped bybiffing or other treatments. This can improve the adhesion between thetire inner periphery and the sealant.

An example of a production facility used in the method for producing aself-sealing tire will be briefly described below referring to FIG. 7.

The production facility includes a twin screw kneading extruder 60, amaterial feeder 62 for supplying raw materials to the twin screwkneading extruder 60, and a rotary drive device 50 which fixes androtates a tire 10 while moving the tire in the width and radialdirections of the tire. The twin screw kneading extruder 60 has fivesupply ports 61, specifically, including three upstream supply ports 61a, one midstream supply port 61 b, and one downstream supply port 61 c.Further, the outlet of the twin screw kneading extruder 60 is connectedto a nozzle 30.

The raw materials are sequentially supplied from the material feeder 62to the twin screw kneading extruder 60 through the supply ports 61 ofthe twin screw kneading extruder 60 and then kneaded in the twin screwkneading extruder 60 to sequentially prepare a sealant. The preparedsealant is continuously discharged from the nozzle 30 connected to theoutlet of the twin screw kneading extruder 60. The tire is traversedand/or moved up and down (moved in the width direction and/or the radialdirection of the tire) while being rotated by the tire drive device, andthe sealant discharged from the nozzle 30 is sequentially applieddirectly to the inner periphery of the tire, whereby the sealant can becontinuously and spirally attached to the tire inner periphery. In otherwords, the sealant can be continuously and spirally attached to theinner periphery of the tire in the tire width direction from one side tothe other by sequentially applying the sealant continuously dischargedfrom the continuous kneader (especially twin screw kneading extruder)directly to the inner periphery of the tire while rotating the tire andsimultaneously moving it in the width direction and/or the radialdirection of the tire.

Such a continuous and spiral attachment of the sealant to the tire innerperiphery can prevent deterioration of tire uniformity, thereby allowingfor the production of a self-sealing tire that is excellent in weightbalance. Moreover, the continuous and spiral attachment of the sealantto the tire inner periphery allows for the formation of a sealant layerin which the sealant is uniformly provided in the circumferential andwidth directions of the tire, and especially in the circumferentialdirection of the tire. This allows for stable production of self-sealingtires having excellent sealing performance with high productivity. Thesealant is preferably attached without overlapping in the widthdirection and more preferably without gaps. In this case, thedeterioration of tire uniformity can be further prevented and a moreuniform sealant layer can be formed.

The raw materials are sequentially supplied to a continuous kneader(especially twin screw kneading extruder) which sequentially prepares asealant. The prepared sealant is continuously discharged from a nozzleconnected to the outlet of the continuous kneader (especially twin screwkneading extruder), and the discharged sealant is sequentially applieddirectly to the inner periphery of a tire. In this manner, self-sealingtires can be produced with high productivity.

The sealant layer is preferably formed by continuously and spirallyapplying a generally string-shaped sealant to the inner periphery of atire. In this case, a sealant layer formed of a generally string-shapedsealant provided continuously and spirally along the inner periphery ofa tire can be formed on the inner periphery of the tire. The sealantlayer may be formed of layers of the sealant, but preferably consists ofone layer of the sealant.

In the case of a generally string-shaped sealant, a sealant layerconsisting of one layer of the sealant can be formed by continuously andspirally applying the sealant to the inner periphery of a tire. In thecase of a generally string-shaped sealant, since the applied sealant hasa certain thickness, even a sealant layer consisting of one layer of thesealant can prevent deterioration of tire uniformity and allows for theproduction of a self-sealing tire having an excellent weight balance andgood sealing performance. Moreover, since it is sufficient to only applyone layer of the sealant without stacking layers of the sealant,self-sealing tires can be produced with higher productivity.

The number of turns of the sealant around the inner periphery of thetire is preferably 20 to 70, more preferably 20 to 60, still morepreferably 35 to 50, because then the deterioration of tire uniformitycan be prevented and a self-sealing tire having an excellent weightbalance and good sealing performance can be produced with higherproductivity. Here, two turns means that the sealant is applied suchthat it makes two laps around the inner periphery of the tire. In FIG.4, the number of turns of the sealant is six.

The use of a continuous kneader (especially twin screw kneadingextruder) enables the preparation (kneading) of a sealant and thedischarge (application) of the sealant to be simultaneously andcontinuously performed. Thus, a highly viscous and adhesive sealantwhich is difficult to handle can be directly applied to the innerperiphery of a tire without handling it, so that a self-sealing tire canbe produced with high productivity. If a sealant is prepared by kneadingwith a curing agent in a batch kneader, the time period from preparing asealant to attaching the sealant to a tire is not constant. In contrast,by sequentially preparing a sealant by mixing raw materials including anorganic peroxide using a continuous kneader (especially twin screwkneading extruder), and sequentially applying the sealant to the innerperiphery of a tire, the time period from preparing a sealant toattaching the sealant to a tire is held constant. Accordingly, when thesealant is applied through a nozzle, the amount of the sealantdischarged from the nozzle is stable; furthermore, the sealant showsconsistent adhesion while reducing the deterioration of adhesion to thetire, and even a highly viscous and adhesive sealant which is difficultto handle can be precisely applied to the tire inner periphery.Therefore, self-sealing tires of a consistent quality can be stablyproduced.

The following describes methods for applying the sealant to the innerperiphery of a tire.

First Embodiment

According to a first embodiment, a self-sealing tire can be produced,for example, by performing the Steps (1), (2), and (3) below in theprocess of applying an adhesive sealant through a nozzle to the innerperiphery of a tire while rotating the tire and simultaneously moving atleast one of the tire and nozzle in the width direction of the tire:Step (1) of measuring the distance between the inner periphery of thetire and the tip of the nozzle using a non-contact displacement sensor;Step (2) of moving at least one of the tire and nozzle in the radialdirection of the tire according to the measurement to adjust thedistance between the inner periphery of the tire and the tip of thenozzle to a predetermined length; and Step (3) of applying the sealantto the inner periphery of the tire after the distance is adjusted.

The distance between the inner periphery of the tire and the tip of thenozzle can be maintained at a constant length by measuring the distancebetween the inner periphery of the tire and the tip of the nozzle usinga non-contact displacement sensor and feeding back the measurement.Moreover, since the sealant is applied to the tire inner periphery whilemaintaining the distance at a constant length, the applied sealant canhave a uniform thickness without being affected by variations in tireshape and irregularities at joint portions or the like. Furthermore,since it is not necessary to enter the coordinate data of each tirehaving a different size as in the conventional art, the sealant can beefficiently applied.

FIG. 1 is an explanatory view schematically showing an example of anapplicator used in a method for producing a self-sealing tire, and FIG.2 is an enlarged view showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1.

FIG. 1 shows a cross section of a part of a tire 10 in the meridionaldirection (a cross section taken along a plane including the width andradial directions of the tire). FIG. 2 shows a cross section of a partof the tire 10 taken along a plane including the circumferential andradial directions of the tire. In FIGS. 1 and 2, the width direction(axis direction) of the tire is indicated by an arrow X, thecircumferential direction of the tire is indicated by an arrow Y, andthe radial direction of the tire is indicated by an arrow Z.

The tire 10 is mounted on a rotary drive device (not shown) which fixesand rotates a tire while moving the tire in the width and radialdirections of the tire. The rotary drive device allows for the followingindependent operations: rotation around the axis of the tire, movementin the width direction of the tire, and movement in the radial directionof the tire.

The rotary drive device includes a controller (not shown) capable ofcontrolling the amount of movement in the radial direction of the tire.The controller may be capable of controlling the amount of movement inthe tire width direction and/or the rotational speed of the tire.

A nozzle 30 is attached to the tip of an extruder (not shown) and can beinserted into the inside of the tire 10. Then an adhesive sealant 20extruded from the extruder is discharged from the tip 31 of the nozzle30.

A non-contact displacement sensor 40 is attached to the nozzle 30 tomeasure the distance d between the inner periphery 11 of the tire 10 andthe tip 31 of the nozzle 30.

Thus, the distance d to be measured by the non-contact displacementsensor is the distance in the radial direction of the tire between theinner periphery of the tire and the tip of the nozzle.

According to the method for producing a self-sealing tire of thisembodiment, the tire 10 formed through a vulcanization step is firstmounted on the rotary drive device, and the nozzle 30 is inserted intothe inside of the tire 10. Then, as shown in FIGS. 1 and 2, the tire 10is rotated and simultaneously moved in the width direction while thesealant 20 is discharged from the nozzle 30, whereby the sealant iscontinuously applied to the inner periphery 11 of the tire 10. The tire10 is moved in the width direction according to the pre-entered profileof the inner periphery 11 of the tire 10.

The sealant 20 preferably has a generally string shape as describedlater. More specifically, the sealant preferably maintains a generallystring shape when the sealant is applied to the inner periphery of thetire. In this case, the generally string-shaped sealant 20 iscontinuously and spirally attached to the inner periphery 11 of the tire10.

The generally string shape as used herein refers to a shape having acertain width, a certain thickness, and a length longer than the width.FIG. 4 schematically shows an example of a generally string-shapedsealant continuously and spirally attached to the inner periphery of atire, and FIG. 8 schematically shows an example of a cross section ofthe sealant shown in FIG. 4 when the sealant is cut along the straightline A-A orthogonal to the direction along which the sealant is applied(longitudinal direction). Thus, the generally string-shaped sealant hasa certain width (length indicated by W in FIG. 8) and a certainthickness (length indicated by D in FIG. 8). The width of the sealantmeans the width of the applied sealant. The thickness of the sealantmeans the thickness of the applied sealant, more specifically thethickness of the sealant layer.

Specifically, the generally string-shaped sealant is a sealant having athickness (thickness of the applied sealant or the sealant layer, lengthindicated by Din FIG. 8) satisfying a preferable numerical range and awidth (width of the applied sealant, length indicated by W in FIG. 4 orW₀ in FIG. 6) satisfying a preferable numerical range as describedlater, and more preferably a sealant having a ratio of the thickness tothe width of the sealant [(thickness of sealant)/(width of sealant)]satisfying a preferable numerical range as described later. Thegenerally string-shaped sealant is also a sealant having across-sectional area satisfying a preferable numerical range asdescribed later.

According to the method for producing a self-sealing tire of thisembodiment, the sealant is applied to the inner periphery of a tire bythe following Steps (1) to (3).

<Step (1)>

As shown in FIG. 2, the distance d between the inner periphery 11 of thetire 10 and the tip 31 of the nozzle 30 is measured with the non-contactdisplacement sensor 40 before the application of the sealant 20. Thedistance d is measured for every tire 10 to whose inner periphery 11 isapplied the sealant 20, from the start to the end of application of thesealant 20.

<Step (2)>

The distance d data is transmitted to the controller of the rotary drivedevice. According to the data, the controller controls the amount ofmovement in the radial direction of the tire so that the distancebetween the inner periphery 11 of the tire 10 and the tip 31 of thenozzle 30 is adjusted to a predetermined length.

<Step (3)>

Since the sealant 20 is continuously discharged from the tip 31 of thenozzle 30, it is applied to the inner periphery 11 of the tire 10 afterthe above distance is adjusted. Through the above Steps (1) to (3), thesealant 20 having a uniform thickness can be applied to the innerperiphery 11 of the tire 10.

FIG. 3 is an explanatory view schematically showing the positionalrelationship of the nozzle to the tire.

As shown in FIG. 3, the sealant can be applied while maintaining thedistance between the inner periphery 11 of the tire 10 and the tip 31 ofthe nozzle 30 at a predetermined distance d₀ during the movement of thenozzle 30 to positions (a) to (d) relative to the tire 10.

When the application of the sealant to the inner periphery of the tireis ended, by adjusting the distance between the inner periphery 11 ofthe tire 10 and the tip 31 of the nozzle 30 to 0, the application of thesealant can be ended while reducing poor application.

To provide more suitable effects, the controlled distance d₀ ispreferably 0.3 mm or more, more preferably 1.0 mm or more. If thedistance is less than 0.3 mm, the tip of the nozzle is too close to theinner periphery of the tire, which makes it difficult to allow theapplied sealant to have a predetermined thickness. The controlleddistance d₀ is also preferably 3.0 mm or less, more preferably 2.0 mm orless. If the distance is more than 3.0 mm, the sealant may not beattached well to the tire, thereby resulting in reduced productionefficiency.

The controlled distance d₀ refers to the distance in the radialdirection of the tire between the inner periphery of the tire and thetip of the nozzle after the distance is controlled in Step (2).

To provide more suitable effects, the controlled distance d₀ ispreferably 30% or less, more preferably 20% or less of the thickness ofthe applied sealant. The controlled distance d₀ is also preferably 5% ormore, more preferably 10% or more of the thickness of the appliedsealant.

The thickness of the sealant (thickness of the applied sealant or thesealant layer, length indicated by D in FIG. 8) is not particularlylimited. To provide more suitable effects, the thickness of the sealantis preferably 1.0 mm or more, more preferably 1.5 mm or more, still morepreferably 2.0 mm or more, particularly preferably 2.5 mm or more. Also,the thickness of the sealant is preferably 10 mm or less, morepreferably 8.0 mm or less, still more preferably 5.0 mm or less. If thethickness is less than 1.0 mm, then a puncture hole formed in the tireis difficult to reliably seal. Also, a thickness of more than 10 mm isnot preferred because tire weight increases, although with littleimprovement in the effect of sealing puncture holes. The thickness ofthe sealant can be controlled by varying the rotational speed of thetire, the velocity of movement in the tire width direction, the distancebetween the tip of the nozzle and the inner periphery of the tire, orother factors.

The sealant preferably has a substantially constant thickness (thicknessof the applied sealant or the sealant layer). In this case, thedeterioration of tire uniformity can be further prevented and aself-sealing tire having much better weight balance can be produced.

The substantially constant thickness as used herein means that thethickness varies within a range of 90% to 110%, preferably 95% to 105%,more preferably 98% to 102%, still more preferably 99% to 101%.

In order to reduce clogging of the nozzle so that excellent operationalstability can be obtained and to provide more suitable effects, agenerally string-shaped sealant is preferably used and more preferablyspirally attached to the inner periphery of the tire. However, a sealantnot having a generally string shape may also be used and applied byspraying onto the tire inner periphery.

In the case of a generally string-shaped sealant, the width of thesealant (width of the applied sealant, length indicated by W in FIG. 4)is not particularly limited. To provide more suitable effects, the widthof the sealant is preferably 0.8 mm or more, more preferably 1.3 mm ormore, still more preferably 1.5 mm or more. If the width is less than0.8 mm, the number of turns of the sealant around the tire innerperiphery may increase, reducing production efficiency. The width of thesealant is also preferably 18 mm or less, more preferably 13 mm or less,still more preferably 9.0 mm or less, particularly preferably 7.0 mm orless, most preferably 6.0mm or less, still most preferably 5.0 mm orless. If the width is more than 18 mm, a weight imbalance may be morelikely to occur.

The ratio of the thickness of the sealant (thickness of the appliedsealant or the sealant layer, length indicated by D in FIG. 8) to thewidth of the sealant (width of the applied sealant, length indicated byW in FIG. 4) [(thickness of sealant)/(width of sealant)] is preferably0.6 to 1.4, more preferably 0.7 to 1.3, still more preferably 0.8 to1.2, particularly preferably 0.9 to 1.1. A ratio closer to 1.0 resultsin a sealant having an ideal string shape so that a self-sealing tirehaving high sealing performance can be produced with higherproductivity.

To provide more suitable effects, the cross-sectional area of thesealant (cross-sectional area of the applied sealant, area calculated byD×W in FIG. 8) is preferably 0.8 mm² or more, more preferably 1.95 mm²or more, still more preferably 3.0 mm² or more, particularly preferably3.75 mm² or more, but preferably 180 mm² or less, more preferably 104mm² or less, still more preferably 45 mm² or less, particularlypreferably 35 mm² or less, most preferably 25 mm² or less.

The width of the area where the sealant is attached (the length of thesealant layer in the tire width direction, hereinafter also referred toas the width of the attachment area or the width of the sealant layer,and corresponding to a length equal to 6×W in FIG. 4 or a length equalto W₁+6×W₀ in FIG. 6) is not particularly limited. To provide moresuitable effects, the width is preferably 80% or more, more preferably90% or more, still more preferably 100% or more, but preferably 120% orless, more preferably 110% or less, of the tread contact width.

To provide more suitable effects, the width of the sealant layer ispreferably 85% to 115%, more preferably 95% to 105% of the width of thebreaker of the tire (the length of the breaker in the tire widthdirection).

Herein, when the tire is provided with a plurality of breakers, thelength of the breaker in the tire width direction refers to the lengthin the tire width direction of the breaker that is the longest in thetire width direction, among the plurality of breakers.

Herein, the tread contact width is determined as follows. First, ano-load and normal condition tire with a normal internal pressuremounted on a normal rim is contacted with a plane at a camber angle of 0degrees while a normal load is applied to the tire, and then the axiallyoutermost contact positions of the tire are each defined as “contactedge Te”. The distance in the tire axis direction between the contactedges Te and Te is defined as a tread contact width TW. The dimensionsand other characteristics of tire components are determined under theabove normal conditions, unless otherwise stated.

The “normal rim” refers to a rim specified for each tire by standards ina standard system including standards according to which tires areprovided, and may be “standard rim” in JATMA, “design rim” in TRA, or“measuring rim” in ETRTO. Moreover, the “normal internal pressure”refers to an air pressure specified for each tire by standards in astandard system including standards according to which tires areprovided, and may be “maximum air pressure” in JATMA, a maximum valueshown in Table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” inTRA, or “inflation pressure” in ETRTO. In the case of tires forpassenger vehicles, the normal internal pressure is 180 kPa.

The “normal load” refers to a load specified for each tire by standardsin a standard system including standards according to which tires areprovided, and may be “maximum load capacity” in JATMA, a maximum valueshown in Table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” inTRA, or “load capacity” in ETRTO. In the case of tires for passengervehicles, the normal load is 88% of the above-specified load.

The rotational speed of the tire during the application of the sealantis not particularly limited. To provide more suitable effects, therotational speed is preferably 5 m/min or higher, more preferably 10m/min or higher, but preferably 30 m/min or lower, more preferably 20m/min or lower. If the rotational speed is lower than 5 m/min or higherthan 30 m/min, a sealant having a uniform thickness cannot be easilyapplied.

When a non-contact displacement sensor is used, the risk of troublescaused by adhesion of the sealant to the sensor can be reduced. Thenon-contact displacement sensor is not particularly limited as long asthe sensor can measure the distance between the inner periphery of thetire and the tip of the nozzle. Examples include laser sensors,photosensors, and capacitance sensors. These sensors may be used aloneor in combinations of two or more. For measurement of rubber, lasersensors or photosensors are preferred among these, with laser sensorsbeing more preferred. When a laser sensor is used, the distance betweenthe inner periphery of the tire and the tip of the nozzle can bedetermined as follows: the inner periphery of the tire is irradiatedwith a laser; the distance between the inner periphery of the tire andthe tip of the laser sensor is determined based on the reflection of thelaser; and the distance between the tip of the laser sensor and the tipof the nozzle is subtracted from the determined distance.

The location of the non-contact displacement sensor is not particularlylimited as long as the distance between the inner periphery of the tireand the tip of the nozzle before the application of the sealant can bemeasured. The sensor is preferably attached to the nozzle, morepreferably in a location to which the sealant will not adhere.

The number, size, and other conditions of the non-contact displacementsensor are also not particularly limited.

Since the non-contact displacement sensor is vulnerable to heat, thesensor is preferably protected with a heat insulator or the like and/orcooled with air or the like to avoid the influence of heat from the hotsealant discharged from the nozzle. This improves the durability of thesensor.

Although the first embodiment has been described based on an example inwhich the tire, not the nozzle, is moved in the width and radialdirections of the tire, the nozzle, not the tire, may be moved, or boththe tire and the nozzle may be moved.

The rotary drive device preferably includes a means to increase thewidth of a tire at a bead portion. In the application of the sealant toa tire, increasing the width of the tire at a bead portion allows thesealant to be easily applied to the tire. Particularly when the nozzleis introduced near the inner periphery of the tire mounted on the rotarydrive device, the nozzle can be introduced only by parallel movement ofthe nozzle, which facilitates the control and improves productivity.

Any means that can increase the width of a tire at a bead portion can beused as the means to increase the width of a tire at a bead portion.Examples include a mechanism in which two devices each having aplurality of (preferably two) rolls which have a fixed positionalrelationship with each other are used and the devices move in the tirewidth direction. The devices maybe inserted from both sides through theopening of the tire into the inside and allowed to increase the width ofthe tire at a bead portion.

In the production method, since the sealant which has been mixed in, forexample, a twin screw kneading extruder and in which the crosslinkingreaction in the extruder is suppressed is directly applied to the tireinner periphery, the crosslinking reaction begins upon the applicationand the sealant adheres well to the tire inner periphery and, at thesame time, the crosslinking reaction more suitably proceeds, whereby aself-sealing tire having high sealing performance can be produced. Thus,the self-sealing tire with the sealant applied thereto does not needfurther crosslinking, thereby offering good productivity.

The self-sealing tire with the sealant applied thereto maybe furthersubjected to a crosslinking step, if necessary.

The self-sealing tire is preferably heated in the crosslinking step.This improves the rate of crosslinking of the sealant and allows thecrosslinking reaction to more suitably proceed so that the self-sealingtire can be produced with higher productivity. The tire may be heated byany method, including known methods, but it may suitably be heated in anoven. The crosslinking step may be carried out, for example, by placingthe self-sealing tire in an oven at 70° C. to 190° C., preferably 150°C. to 190° C., for 2 to 15 minutes.

The tire is preferably rotated in the circumferential direction of thetire during the crosslinking because then flowing of even thejust-applied, easily flowing sealant can be prevented and thecrosslinking reaction can be accomplished without deterioration ofuniformity. The rotational speed is preferably 300 to 1,000 rpm.Specifically, for example, an oven equipped with a rotational mechanismmay be used.

Even when the crosslinking step is not additionally performed, the tireis preferably rotated in the circumferential direction of the tire untilthe crosslinking reaction of the sealant is completed. In this case,flowing of even the just-applied, easily flowing sealant can beprevented and the crosslinking reaction can be accomplished withoutdeterioration of uniformity. The rotational speed is the same asdescribed for the crosslinking step.

In order to improve the rate of crosslinking of the sealant, the tire ispreferably preliminarily warmed before the application of the sealant.This allows for the production of self-sealing tires with higherproductivity. The temperature for pre-heating the tire is preferably 40°C. to 100° C., more preferably 50° C. to 70° C. When the tire ispre-heated within the temperature range indicated above, thecrosslinking reaction suitably begins upon the application and moresuitably proceeds so that a self-sealing tire having high sealingperformance can be produced. Moreover, when the tire is pre-heatedwithin the temperature range indicated above, the crosslinking step isnot necessary and thus the self-sealing tire can be produced with highproductivity.

In general, continuous kneaders (especially twin screw kneadingextruders) are continuously operated. In the production of self-sealingtires, however, tires need to be replaced one after another uponcompletion of the application of the sealant to one tire. Here, in orderto produce higher quality self-sealing tires while reducingdeterioration of productivity, the following method (1) or (2) maybeused. The method (1) or (2) may be appropriately selected depending onthe situation, in view of the following disadvantages: deterioration inquality in the method (1) and an increase in cost in the method (2).

(1) The feed of the sealant to the inner periphery of the tire iscontrolled by running or stopping the continuous kneader and all thefeeders simultaneously.

Specifically, upon completion of the application to one tire, thecontinuous kneader and all the feeders may be simultaneously stopped,the tire may be replaced with another tire, preferably within oneminute, and the continuous kneader and all the feeders may besimultaneously allowed to run to restart the application to the tire. Byreplacing tires quickly, preferably within one minute, the deteriorationin quality can be reduced.

(2) The feed of the sealant to the inner periphery of the tire iscontrolled by switching flow channels while allowing the continuouskneader and all the feeders to keep running.

Specifically, the continuous kneader may be provided with another flowchannel in addition to the nozzle for direct feeding to the tire innerperiphery, and the prepared sealant may be discharged from the anotherflow channel after completion of the application to one tire untilcompletion of the replacement of tires. According to this method, sinceself-sealing tires can be produced while the continuous kneader and allthe feeders are kept running, the produced self-sealing tires can havehigher quality.

Non-limiting examples of carcass cords that can be used in the carcassof the self-sealing tire described above include fiber cords and steelcords. Steel cords are preferred among these. In particular, steel cordsformed of hard steel wire materials specified in JIS G 3506 aredesirable. The use of strong steel cords, instead of commonly used fibercords, as carcass cords in the self-sealing tire can greatly improveside cut resistance (resistance to cuts formed in the tire side portionsdue to driving over curbs or other reasons) and thereby further improvethe puncture resistance of the entire tire including the side portions.

The steel cord may have any structure. Examples include steel cordshaving a 1×n single strand structure, steel cords having a k+m layerstrand structure, steel cords having a 1×n bundle structure, and steelcords having an m×n multi-strand structure. The term “steel cord havinga 1×n single strand structure” refers to a single-layered twisted steelcord prepared by intertwining n filaments. The term “steel cord having ak+m layer strand structure” refers to a steel cord having a two-layeredstructure in which the two layers are different from each other in twistdirection and twist pitch, and the inner layer includes k filamentswhile the outer layer includes m filaments. The term “steel cord havinga 1×n bundle structure” refers to a bundle steel cord prepared byintertwining bundles of n filaments. The term “steel cord having an m xn multi-strand structure” refers to a multi-strand steel cord preparedby intertwining m strands prepared by first twisting n filamentstogether. Here, n represents an integer of 1 to 27; k represents aninteger of 1 to 10; and m represents an integer of 1 to 3.

The twist pitch of the steel cord is preferably 13 mm or less, morepreferably 11 mm or less, but preferably 5mm or more, more preferably 7mm or more.

The steel cord preferably contains at least one piece of preformedfilament formed in the shape of a spiral. Such a preformed filamentprovides a relatively large gap within the steel cord to improve rubberpermeability and also maintain the elongation under low load, so that amolding failure during vulcanization can be prevented.

The surface of the steel cord is preferably plated with brass, Zn, orother materials to improve initial adhesion to the rubber composition.

The steel cord preferably has an elongation of 0.5% to 1.5% under a loadof 50 N. If the elongation under a load of 50 N is more than 1.5%, thereinforcing cords may exhibit reduced elongation under high load andthus disturbance absorption may not be maintained. Conversely, if theelongation under a load of 50 N is less than 0.5%, the cords may notshow sufficient elongation during vulcanization and thus a moldingfailure may occur. In view of the above, the elongation under a load of50 N is more preferably 0.7% or more, but more preferably 1.3% or less.

The endcount of the steel cords is preferably 20 to 50 (ends/5 cm).

Second Embodiment

The studies of the present inventors have further revealed that the useof the method according to the first embodiment alone has the followingdisadvantage: a sealant having a generally string shape is occasionallydifficult to attach to the inner periphery of a tire and can easily peeloff especially at the attachment start portion. A second embodiment ischaracterized in that in the method for producing a self-sealing tire,the sealant is attached under conditions where the distance between theinner periphery of the tire and the tip of the nozzle is adjusted to adistance d₁ and then to a distance d₂ larger than the distance d₁. Inthis case, the distance between the inner periphery of the tire and thetip of the nozzle is shortened at the beginning of the attachment, sothat the width of the sealant corresponding to the attachment startportion can be increased. As a result, a self-sealing tire can be easilyproduced in which a generally string-shaped adhesive sealant iscontinuously and spirally attached at least to the inner periphery ofthe tire that corresponds to a tread portion, and at least one of thelongitudinal ends of the sealant forms a wider portion having a widthlarger than that of the longitudinally adjoining portion. In thisself-sealing tire, a portion of the sealant that corresponds to startingof attachment has a larger width to improve adhesion of this portion sothat peeling of this portion of the sealant can be prevented.

The description of the second embodiment basically includes onlyfeatures different from the first embodiment, and the contentsoverlapping the description of the first embodiment are omitted.

FIG. 5 are enlarged views showing the vicinity of the tip of the nozzleincluded in the applicator shown in FIG. 1. FIG. 5(a) illustrates astatus immediately after attachment of the sealant is started and FIG.5(b) illustrates a status after a lapse of a predetermined time.

FIG. 5 each show a cross section of a part of a tire 10 taken along aplane including the circumferential and radial directions of the tire.In FIG. 5, the width direction (axis direction) of the tire is indicatedby an arrow X, the circumferential direction of the tire is indicated byan arrow Y, and the radial direction of the tire is indicated by anarrow Z.

According to the second embodiment, the tire 10 formed through avulcanization step is first mounted on a rotary drive device, and anozzle 30 is inserted into the inside of the tire 10. Then, as shown inFIGS. 1 and 5, the tire 10 is rotated and simultaneously moved in thewidth direction while a sealant 20 is discharged from the nozzle 30,whereby the sealant is continuously applied to the inner periphery 11 ofthe tire 10. The tire 10 is moved in the width direction according to,for example, the pre-entered profile of the inner periphery 11 of thetire 10.

Since the sealant 20 is adhesive and has a generally string shape, thesealant 20 is continuously and spirally attached to the inner periphery11 of the tire 10 that corresponds to a tread portion.

In this process, as shown in FIG. 5(a), the sealant 20 is attached underconditions where the distance between the inner periphery 11 of the tire10 and the tip 31 of the nozzle 30 is adjusted to a distance d₁ for apredetermined time from the start of the attachment. Then, after a lapseof the predetermined time, as shown in FIG. 5(b), the tire 10 is movedin the radial direction to change the distance to a distance d₂ largerthan the distance d₁ and the sealant 20 is attached.

The distance may be changed from the distance d₂ back to the distance d₁before completion of the attachment of the sealant. In view ofproduction efficiency and tire weight balance, the distance d₂ ispreferably maintained until the sealant attachment is completed.

Preferably, the distance d₁ is kept constant for a predetermined timefrom the start of the attachment, and after a lapse of the predeterminedtime the distance d₂ is kept constant, although the distances d₁ and d₂are not necessarily constant as long as they satisfy the relation ofd₁<d₂.

The distance d₁ is not particularly limited. To provide more suitableeffects, the distance d₁ is preferably 0.3 mm or more, more preferably0.5 mm or more. If the distance d₁ is less than 0.3mm, the tip of thenozzle is too close to the inner periphery of the tire, so that thesealant can easily adhere to the nozzle and the nozzle may need to becleaned more frequently. The distance d₁ is also preferably 2 mm orless, more preferably 1 mm or less. If the distance d₁ is more than 2mm, the effect produced by the formation of a wider portion may not besufficient.

The distance d₂ is also not particularly limited. To provide moresuitable effects, the distance d₂ is preferably 0.3 mm or more, morepreferably 1 mm or more, but preferably 3 mm or less, more preferably 2mm or less. The distance d₂ is preferably the same as the controlleddistance d₀ described above.

Herein, the distances d₁ and d₂ between the inner periphery of the tireand the tip of the nozzle each refer to the distance in the radialdirection of the tire between the inner periphery of the tire and thetip of the nozzle.

The rotational speed of the tire during the attachment of the sealant isnot particularly limited. To provide more suitable effects, therotational speed is preferably 5 m/min or higher, more preferably 10m/min or higher, but preferably 30 m/min or lower, more preferably 20m/min or lower. If the rotational speed is lower than 5 m/min or higherthan 30 m/min, a sealant having a uniform thickness cannot be easilyattached.

The self-sealing tire according to the second embodiment can be producedthrough the steps described above.

FIG. 6 is an explanatory view schematically showing an example of asealant attached to a self-sealing tire according to the secondembodiment.

The generally string-shaped sealant 20 is wound in the circumferentialdirection of the tire and continuously and spirally attached. Here, oneof the longitudinal ends of the sealant 20 forms a wider portion 21having a width larger than that of the longitudinally adjoining portion.The wider portion 21 corresponds to the attachment start portion of thesealant.

The width of the wider portion of the sealant (width of the widerportion of the applied sealant, length indicated by W₁ in FIG. 6) is notparticularly limited. To provide more suitable effects, the width of thewider portion is preferably 103% or more, more preferably 110% or more,still more preferably 120% or more of the width of the sealant otherthan the wider portion (length indicated by W₀ in FIG. 6). If it is lessthan 103%, the effect produced by the formation of a wider portion maynot be sufficient. The width of the wider portion of the sealant is alsopreferably 210% or less, more preferably 180% or less, still morepreferably 160% or less of the width of the sealant other than the widerportion. If it is more than 210%, the tip of the nozzle needs to beplaced excessively close to the inner periphery of the tire to form awider portion, with the result that the sealant can easily adhere to thenozzle and the nozzle may need to be cleaned more frequently. Inaddition, tire weight balance may be impaired.

The width of the wider portion of the sealant is preferablysubstantially constant in the longitudinal direction but may partiallybe substantially not constant. For example, the wider portion may have ashape in which the width is the largest at the attachment start portionand gradually decreases in the longitudinal direction. The substantiallyconstant width as used herein means that the width varies within a rangeof 90% to 110%, preferably 97% to 103%, more preferably 98% to 102%,still more preferably 99% to 101%.

The length of the wider portion of the sealant (length of the widerportion of the applied sealant, length indicated by L₁ in FIG. 6) is notparticularly limited. To provide more suitable effects, the length ispreferably less than 650 mm, more preferably less than 500 mm, stillmore preferably less than 350 mm, particularly preferably less than 200mm. If the length is 650 mm or more, the tip of the nozzle is placedclose to the inner periphery of the tire for a longer period of time, sothat the sealant can easily adhere to the nozzle and the nozzle may needto be cleaned more frequently. In addition, tire weight balance may beimpaired. The sealant preferably has a shorter wider portion. However,for control of the distance between the inner periphery of the tire andthe tip of the nozzle, the limit of the length of the wider portion isabout 10 mm.

The width of the sealant other than the wider portion (width of theapplied sealant other than the wider portion, length indicated by W₀ inFIG. 6) is not particularly limited. To provide more suitable effects,the width is preferably 0.8 mm or more, more preferably 1.3 mm or more,still more preferably 1.5 mm or more. If the width is less than 0.8 mm,the number of turns of the sealant around the inner periphery of thetire may increase, reducing production efficiency. The width of thesealant other than the wider portion is also preferably 18 mm or less,more preferably 13 mm or less, still more preferably 9.0 mm or less,particularly preferably 7.0 mm or less, most preferably 6.0 mm or less,still most preferably 5.0 mm or less. If the width is more than 18 mm, aweight imbalance may be more likely to occur. W₀ is preferably the sameas the above-described W.

The width of the sealant other than the wider portion is preferablysubstantially constant in the longitudinal direction but may partiallybe substantially not constant.

The width of the area where the sealant is attached (the length of thesealant layer in the tire width direction, hereinafter also referred toas the width of the attachment area or the width of the sealant layer,and corresponding to a length equal to W₁+6×W₀ in FIG. 6) is notparticularly limited. To provide more suitable effects, the width ispreferably 80% or more, more preferably 90% or more, still morepreferably 100% or more, but preferably 120% or less, more preferably110% or less, of the tread contact width.

To provide more suitable effects, the width of the sealant layer ispreferably 85% to 115%, more preferably 95% to 105% of the width of thebreaker of the tire (the length of the breaker in the tire widthdirection).

In the self-sealing tire according to the second embodiment, the sealantis preferably attached without overlapping in the width direction andmore preferably without gaps.

In the self-sealing tire according to the second embodiment, the otherlongitudinal end (the end corresponding to the attachment endingportion) of the sealant may also form a wider portion having a widthlarger than that of the longitudinally adjoining portion.

The thickness of the sealant (thickness of the applied sealant or thesealant layer, length indicated by D in FIG. 8) is not particularlylimited. To provide more suitable effects, the thickness of the sealantis preferably 1.0 mm or more, more preferably 1.5 mm or more, still morepreferably 2.0 mm or more, particularly preferably 2.5 mm or more, butpreferably 10 mm or less, more preferably 8.0 mm or less, still morepreferably 5.0 mm or less. If the thickness is less than 1.0 mm, then apuncture hole formed in the tire is difficult to reliably seal. Also, athickness of more than 10 mm is not preferred because tire weightincreases, although with little improvement in the effect of sealingpuncture holes.

The sealant preferably has a substantially constant thickness (thicknessof the applied sealant or the sealant layer). In this case, thedeterioration of tire uniformity can be further prevented and aself-sealing tire having much better weight balance can be produced.

The ratio of the thickness of the sealant (thickness of the appliedsealant or the sealant layer, length indicated by D in FIG. 8) to thewidth of the sealant other than the wider portion (width of the appliedsealant other than the wider portion, length indicated by W₀ in FIG. 6)[(thickness of sealant)/(width of sealant other than wider portion)] ispreferably 0.6 to 1.4, more preferably 0.7 to 1.3, still more preferably0.8 to 1.2, particularly preferably 0.9 to 1.1. A ratio closer to 1.0results in a sealant having an ideal string shape so that a self-sealingtire having high sealing performance can be produced with higherproductivity.

To provide more suitable effects, the cross-sectional area of thesealant (cross-sectional area of the applied sealant, area calculated byD×W in FIG. 8) is preferably 0.8 mm² or more, more preferably 1.95 mm²or more, still more preferably 3.0 mm² or more, particularly preferably3.75 mm² or more, but preferably 180 mm² or less, more preferably 104mm² or less, still more preferably 45 mm² or less, particularlypreferably 35 mm² or less, most preferably 25 mm² or less.

According to the second embodiment, even when the sealant has aviscosity within the range indicated earlier, and particularly arelatively high viscosity, widening a portion of the sealant thatcorresponds to starting of attachment can improve adhesion of thisportion so that peeling of this portion of the sealant can be prevented.

The self-sealing tire according to the second embodiment is preferablyproduced as described above. However, the self-sealing tire may beproduced by any other appropriate method as long as at least one of theends of the sealant is allowed to form a wider portion.

Third Embodiment

The studies of the present inventors have further revealed that the useof the method according to the first embodiment alone has the followingdisadvantage: a sealant having a generally string shape is occasionallydifficult to attach to the inner periphery of a tire and can easily peeloff especially at the attachment start portion. The studies of thepresent inventors have still further revealed that, if the attachmentstart portion of the sealant is peeled, unfortunately the peeled portionmay not show sufficient sealing performance, and thus sufficient sealingperformance cannot be obtained on the entire sealant layer.

In order to solve these problems, the attachment start portion of thesealant is adapted to be located tire-widthwise inward from thetire-widthwise end of the sealant layer as shown in FIG. 10(d). Thisallows the entire sealant layer to have sufficient sealing performanceeven when the attachment start portion of the sealant is peeled.

More specifically, the sealant layer is formed by continuously applyinga generally string-shaped sealant to the inner periphery of a tire fromthe attachment start portion located tire-widthwise inward from thetire-widthwise end of the sealant layer toward the tire-widthwise end ofthe sealant layer, and then continuously and spirally applying agenerally string-shaped sealant to the inner periphery of the tire fromthe tire-widthwise end of the sealant layer toward the othertire-widthwise end of the sealant layer. In this case, the sealant isadditionally applied to the attachment start portion by applying thesealant from one tire-widthwise end of the sealant layer toward theother tire-widthwise end of the sealant layer. As a result, the entiresealant layer can have sufficient sealing performance even when theattachment start portion of the sealant is peeled.

In the method for producing a self-sealing tire according to the thirdembodiment, the attachment start position of the sealant may be settire-widthwise inward from the tire-widthwise end of the sealant layer.More specifically, the method for producing a self-sealing tire may becontrolled such that the attachment start position of the sealant is settire-widthwise inward from the tire-widthwise end of the sealant layer,and the generally string-shaped sealant is continuously applied to theinner periphery of the tire from the attachment start portion toward thetire-widthwise end of the sealant layer, and then continuously andspirally applied to the inner periphery of the tire from thetire-widthwise end of the sealant layer toward the other tire-widthwiseend of the sealant layer. Since the third embodiment is the same as thefirst and second embodiments except for the above features, the thirdembodiment will be basically described only on features which aredifferent from the first and second embodiments. The contentsoverlapping the descriptions of the first and second embodiments areomitted.

As used herein, and particularly in the third embodiment, thetire-widthwise end of the sealant layer refers to the tire-widthwise end(the end located in the tire width direction) of the sealant attachmentarea which is the area where the sealant is applied.

Accordingly, the description “the attachment start position of thesealant is set tire-widthwise inward from the tire-widthwise end of thesealant layer, and the generally string-shaped sealant is continuouslyapplied to the inner periphery of the tire from the attachment startportion toward the tire-widthwise end of the sealant layer, and thencontinuously and spirally applied to the inner periphery of the tirefrom the tire-widthwise end of the sealant layer toward the othertire-widthwise end of the sealant layer” means that the attachment startposition of the sealant is set tire-widthwise inward from thetire-widthwise end of the sealant attachment area, and the generallystring-shaped sealant is continuously applied to the inner periphery ofthe tire from the attachment start portion toward the tire-widthwise endof the sealant attachment area, and then continuously and spirallyapplied to the inner periphery of the tire from the tire-widthwise endof the sealant attachment area toward the other tire-widthwise end ofthe sealant attachment area.

In the third embodiment, in order to reduce deterioration of tireuniformity and in view of productivity such as increase in materialcosts or application time, preferably a smaller amount of the sealant isapplied to the inner periphery of the tire from the attachment startportion toward the tire-widthwise end of the sealant layer. Theapplication amount may be reduced by increasing the rotational speed ofthe tire; however, this may increase the likelihood of peeling of theattachment start portion. In view of this, the velocity of movement inthe tire width direction of the application position (e.g. the nozzle)assumed when the sealant is applied from the attachment start portiontoward the tire-widthwise end of the sealant layer (hereinafter, alsoreferred to as the velocity of application position during forwarding)is preferably increased to shorten the time for the application positionto reach the tire-widthwise end of the sealant layer. This can reducethe application amount while reducing the likelihood of peeling of theattachment start portion.

The velocity of movement in the tire width direction of the applicationposition assumed when the sealant is applied from the attachment startportion toward the tire-widthwise end of the sealant layer is preferably10 to 600 mm/min, more preferably 50 to 450 mm/min, still morepreferably 50 to 300 mm/min, particularly preferably 80 to 120 mm/min.

In order to form a more uniform sealant layer, the velocity of movementin the tire width direction of the application position assumed when thesealant is continuously and spirally applied from the tire-widthwise endof the sealant layer toward the other tire-widthwise end of the sealantlayer (hereinafter, also referred to as the velocity of applicationposition during spiral application) is preferably lower than thevelocity of application position during forwarding. In other words, inorder to reduce deterioration of tire uniformity and in view ofproductivity such as increase in material costs or application time, andof uniformity of the sealant layer, the velocity of application positionduring forwarding is preferably higher than the velocity of applicationposition during spiral application. Specifically, the velocity ofapplication position during forwarding is preferably 1.3 to 6.0 timeshigher, more preferably 2.0 to 4.0 times higher than the velocity ofapplication position during spiral application.

The self-sealing tire according to the third embodiment can be producedthrough the steps described above.

FIG. 10(d) is an explanatory view schematically showing an example of asealant attached to a self-sealing tire according to the thirdembodiment.

The generally string-shaped sealant 20 is wound in the circumferentialdirection of the tire and continuously and spirally attached. The widthfrom the tire-widthwise end of the sealant layer to the attachment startportion of the sealant (inward application width, length indicated byW_(in) in FIG. 10(d)) is not particularly limited. In order to reducedeterioration of tire uniformity and in view of productivity such asincrease in material costs or application time, the width is preferably2 to 40 mm, more preferably 8 to 25 mm.

The inward application width W_(in) is not particularly limited. Inorder to reduce deterioration of tire uniformity and in view ofproductivity such as increase in material costs or application time, thewidth W_(in) is preferably 2.0% to 25%, more preferably 2.0% to 15% ofthe width of the sealant layer.

The width of the sealant, the width of the area where the sealant isattached, the thickness of the sealant, the cross-sectional area of thesealant, and the ratio of the thickness of the sealant to the width ofthe sealant are the same as in the first and second embodiments.

In the self-sealing tire according to the third embodiment, when thesealant is applied from the tire-widthwise end of the sealant layertoward the other tire-widthwise end of the sealant layer, the sealant ispreferably attached without overlapping in the width direction and morepreferably without gaps.

Although the self-sealing tire according to the third embodiment ispreferably produced as described above, it may be produced by any otherappropriate method as long as the attachment start portion of thesealant is allowed to be located tire-widthwise inward from thetire-widthwise end of the sealant layer, and further, as long as theattachment start portion of the sealant is allowed to be locatedtire-widthwise inward from the tire-widthwise end of the sealant layer,and the sealant can be additionally applied to the attachment startportion.

Although the above descriptions, and particularly the description of thefirst embodiment, explain the case where a non-contact displacementsensor is used in applying the sealant to the inner periphery of thetire, the sealant may be applied to the inner periphery of the tirewhile controlling the movement of the nozzle and/or the tire accordingto the pre-entered coordinate data, without measurement using anon-contact displacement sensor.

Self-sealing tires including a sealant layer located radially inside aninnerliner can be produced as described above or by other methods. Thesealant layer is preferably formed by applying a sealant to the innerperiphery of a vulcanized tire because of advantages such as thatproblems caused by flowing of the sealant or other reasons are lesslikely to occur and that this method can be responsive to changes intire size by programming. For easy handling of the sealant and highproductivity, the sealant layer is also preferably formed bysequentially preparing a sealant by mixing raw materials including acrosslinking agent using a continuous kneader, and sequentially applyingthe sealant to the inner periphery of a tire.

The sealant layer in the present invention is characterized particularlyby being formed by applying a sealant to the inner periphery of a tirefrom which mold release agents have been removed.

As described above, in the present invention, since a sealant layer isformed by applying a sealant to the inner periphery of a tire from whichmold release agents have been removed, the adhesion between the sealantand the inner periphery of the tire is improved, and therefore thesealant can be successfully applied to the inner periphery of the tirein the sealant application, and further the sealant does not dislocateor separate during service, thereby causing no vibration but providingsufficient sealing performance.

The sealant layer in the present invention may be formed by any methodas long as it is formed by applying a sealant to the inner periphery ofa tire from which mold release agents have been removed. Preferably, thesealant layer is formed by continuously and spirally applying agenerally string-shaped sealant to the inner periphery of a tire fromwhich mold release agents have been removed, in the tire width directionfrom one side to the other. This allows for stable production ofself-sealing tires having much better sealing performance with highproductivity.

As described above, an innerliner, which is a rubber component formingthe inner periphery of a tire, is made from a rubber having a low airpermeability. It is a tire component provided to ensure air retentionproperties for tires. When mold release agents have been removed fromthe tire inner periphery, e.g. as described above, the tire innerperiphery from which mold release agents have been removed has a scrapedsurface. Thus, the innerliner layer is made thinner and may not ensuresufficient air retention properties due to air leakage from this part.

Since sealants also have low air permeability, if a sealant is appliedto the thinner part of the innerliner layer, the sealant can compensatefor the loss of air retention properties, thereby ensuring air retentionproperties for the tire. For this reason, in the present invention, asealant is preferably applied to the entire area of the inner peripheryof a tire from which mold release agents have been removed. In thiscase, the sealant can supplement air retention properties and allow eventhe thinner innerliner layer to ensure sufficient air retentionproperties. Furthermore, by controlling the length of the sealant layerin the tire width direction and the length in the tire width directionof the area of the inner periphery of the tire from which mold releaseagents have been removed, the self-sealing tire can have a betterbalance of sealing performance and air retention properties.

Specifically, preferably the sealant is applied to the entire area ofthe inner periphery of a tire from which mold release agents have beenremoved, and further, the length of the sealant layer in the tire widthdirection and the length in the tire width direction of the area of theinner periphery of the tire from which mold release agents have beenremoved satisfy the formula below. In this case, better air retentionproperties can be obtained. Moreover, when the lower limit of theformula is preferably more than 0 mm (i.e. 0 mm<), and is morepreferably 1.0 mm, still more preferably 3.0 mm, sealing performance canbe further improved and air retention properties can also be furtherimproved. On the other hand, when the upper limit of the formula is morethan 16.0 mm, the improvement effects reach a plateau with increase inmaterial costs.

0 mm≦(the length of the sealant layer in the tire width direction)−(thelength in the tire width direction of the area from which mold releaseagents have been removed)≦16.0 mm

Preferably, the length in the tire width direction of the area of thesealant layer formed by applying a sealant to the inner periphery of atire from which mold release agents have been removed and the length ofthe breaker of the tire in the tire width direction satisfy the formulabelow. In this case, sealing performance can be further improved. Thelower limit of the formula is preferably more than 0 mm, and is morepreferably 1.0 mm, still more preferably 3.0 mm, particularly preferably5.0 mm. On the other hand, when the upper limit of the formula is morethan 8.0 mm, the improvement effect reaches a plateau with increase inmaterial costs.

The area formed by applying a sealant to the inner periphery of a tirefrom which mold release agents have been removed refers to a portion ofthe sealant layer formed on the area from which mold release agents havebeen removed. In the case where the sealant is applied to the entirearea of the inner periphery of a tire from which mold release agentshave been removed, the length in the tire width direction of the area ofthe sealant layer formed by applying a sealant to the inner periphery ofa tire from which mold release agents have been removed is equal to thelength in the tire width direction of the area from which mold releaseagents have been removed.

0mm≦(the length in the tire width direction of the area of the sealantlayer formed by applying a sealant to the inner periphery of a tire fromwhich mold release agents have been removed)−(the length of the breakerin the tire width direction)≦8.0 mm

The self-sealing tire of the present invention is preferably produced bythe method according to the third embodiment, among the above-describedmethods. In particular, the attachment start portion of the sealant ispreferably located tire-widthwise inward from the tire-widthwise end ofthe sealant layer. More preferably, the sealant layer is formed bycontinuously applying a generally string-shaped sealant to the innerperiphery of a tire from the attachment start portion locatedtire-widthwise inward from the tire-widthwise end of the sealant layertoward the tire-widthwise end of the sealant layer, and thencontinuously and spirally applying a generally string-shaped sealant tothe inner periphery of the tire from the tire-widthwise end of thesealant layer toward the other tire-widthwise end of the sealant layer.In this case, better sealing performance and better air retentionproperties can be obtained, and the application of the sealant to the tothe inner periphery of a tire can be successfully accomplished.

EXAMPLES

The present invention is specifically described with reference to, butnot limited to, examples below.

The chemicals used in the examples are listed below.

Butyl rubber A: Regular butyl 065 (available from Japan Butyl Co., Ltd.,Mooney viscosity ML₁₊₈ at 125° C.: 32)

Liquid polymer A: Nisseki polybutene HV300 (available from JX Nippon Oil& Energy Corporation, kinematic viscosity at 40° C.: 26,000 mm²/s,kinematic viscosity at 100° C.: 590 mm²/s, number average molecularweight: 1,400)

Liquid polymer B: Nisseki polybutene HV1900 (available from JX NipponOil & Energy Corporation, kinematic viscosity at 40° C.: 160,000 mm²/s,kinematic viscosity at 100° C.: 3,710 mm²/s, number average molecularweight: 2,900)

Plasticizer: DOP (dioctyl phthalate, available from Showa Chemical,specific gravity: 0.96, viscosity: 81 mPs·s)

Carbon black: N330 (available from Cabot Japan K.K., HAF grade, DBP oilabsorption: 102 ml/100 g)

Crosslinking activator: VULNOC GM (available from Ouchi Shinko ChemicalIndustrial Co., Ltd., p-benzoquinone dioxime)

Crosslinking agent: NYPER NS (available from NOF Corporation, dibenzoylperoxide (40% dilution, dibenzoyl peroxide: 40%, dibutyl phthalate:48%), the amount shown in Table 1 is the net benzoyl peroxide content)

(Removal of Mold Release Agents)

The tire used in Example 1 was rubbed with a brush for 27 minutes usingnaphtha to wash off the mold release agents adhering to the innerperiphery of the tire.

The tires used in Examples 2 to 10 were subjected to removal of moldrelease agents from the tire inner periphery using a buffing machinewith a polishing brush for 3 minutes.

The removal of mold release agents from each tire was carried out on theentire inner periphery of the tire so that the treated area had a width(buffing width) shown in Table 2.

<Production of Self-Sealing Tire>

According to the formulation in Table 1, the chemicals were introducedinto a twin screw kneading extruder as follows: the butyl rubber A,carbon black, and crosslinking activator were introduced from theupstream supply port; the liquid polybutene B (liquid polymer B) wasintroduced from the midstream supply port; and the liquid polybutene A(liquid polymer A), plasticizer, and crosslinking agent were introducedfrom the downstream supply port. They were kneaded at 200 rpm at abarrel temperature of 100° C. to prepare a sealant. The liquidpolybutenes were heated to 50° C. before the introduction from thesupply ports.

(Time for Kneading Materials)

Time for mixing butyl rubber A, carbon black, and crosslinkingactivator: 2 minutes

Time for mixing liquid polybutene B: 2 minutes

Time for mixing liquid polybutene A, plasticizer, and crosslinkingagent: 1.5 minutes

The sealant (at 100° C.) sequentially prepared as above was extrudedfrom the twin screw kneading extruder through the nozzle andcontinuously and spirally attached (spirally applied) as shown in FIGS.1 to 4 to the inner periphery of a tire (215/55R17, 94W, rim: 17X8J,cross-sectional area of cavity of tire mounted on rim: 194 cm²,vulcanized, pre-heating temperature: 40° C., width of tire breaker: 178mm, rotational speed of tire: 10.4 rpm) mounted on a rotary drivedevice, from one tire-widthwise end of the sealant attachment areatoward the other end at a velocity of movement in the tire widthdirection of the application position set to 26.9 mm/min to allow thesealant (viscosity at 40° C.: 10,000 Pa·s, generally string shape,thickness: 3 mm, width: 4 mm, discharge amount: 9 kg/h) to form asealant layer under the conditions shown in Table 2.

In Example 10, a sealant layer was formed by continuously applying agenerally string-shaped sealant to the inner periphery of the tire fromthe attachment start position located tire-widthwise inward from thetire-widthwise end of the sealant attachment area toward thetire-widthwise end of the sealant attachment area at a velocity ofmovement in the tire width direction of the application position set to107.6 mm/min, followed by continuous and spiral attachment (spiralapplication) to the inner periphery of the tire as shown in FIGS. 1 to 4from one tire-widthwise end of the sealant attachment area toward theother end at a velocity of movement in the tire width direction of theapplication position set to 26.9 mm/min to form a sealant layer.

The width of the sealant was controlled to be substantially constant inthe longitudinal direction. The viscosity of the sealant was measured at40° C. in conformity with JIS K 6833 using a rotational viscometer.

Comparative Example 1

A tire without removal of mold release agents and application of asealant was used in Comparative Example 1.

In Table 2, “Minimum sealant application width” means the width of thesealant layer; “Buffed area≦Sealant area” means (the length in the tirewidth direction of the area from which mold release agents have beenremoved)≦(the length of the sealant layer in the tire width direction);“Sealant/buffed area difference” means [(the length of the sealant layerin the tire width direction)−(the length in the tire width direction ofthe area from which mold release agents have been removed)]; and“Difference between breaker width vs area with both buffing/sealant”means [(the length in the tire width direction of the area of thesealant layer formed by applying a sealant to the inner periphery of atire from which mold release agents have been removed)−(the length ofthe breaker in the tire width direction)].

(Application Success Rate)

The application was performed on ten tires as described above, and thenthe rate of success of one-time application was calculated. Table 2shows the results. A larger figure indicates that the application of asealant to the inner periphery of a tire can be more successfullyaccomplished.

(Air Sealing Rate at Breaker Edge after Running)

The tire produced as described above was rotated on a drum at 100 km/hfor one hour. Then, ten nails with a diameter of 4 mm were driven intothe tread portion corresponding to the tire-widthwise end of the breakerthat was the longest in the tire width direction. After removal of thenails, the rate of successful air sealing was calculated. Table 2 showsthe results. A larger figure indicates better sealing performance,especially at the tire-widthwise end of the breaker that was the longestin the tire width direction.

(Air Leakage Rate)

After the pressure of the tire produced as described above was adjustedto 250 kPa, the tire was allowed to stand at 25° C. for two months.Then, the residual pressure of the tire was measured. The results areexpressed as an index, with the tire (normal tire) of ComparativeExample 1 set equal to 100. A higher index indicates better airretention properties.

TABLE 1 Formulation Butyl rubber A 100 amount (ML₁₊₈ at 125° C.: 32)(parts by mass) Liquid polymer A 100 (Kinematic viscosity at 100° C.:590) Liquid polymer B 100 (Kinematic viscosity at 100° C.: 3710)Plasticizer (DOP) 10 Carbon black (N330) 10 Crosslinking activator 10(p-benzoquinone dioxime) Crosslinking agent 10 (Dibenzoyl peroxide)

It is demonstrated that the self-sealing tires of the examples in whicha sealant layer was formed by applying a sealant to the inner peripheryof a tire from which mold release agents had been removed exhibitedsufficient sealing performance.

In Example 1, since the inner surface of the tire was wiped with anorganic solvent (naphtha), the innerliner layer was less likely to bemade thinner as compared with when a buffing machine was used, and thusthe deterioration of sealing performance was reduced. As a result, theair retention properties were better than in Example 2. However, theprocess in Example 1 takes a long time, thereby reducing productivity.

REFERENCE SIGNS LIST

10 Tire

11 Inner periphery of tire

14 Tread portion

15 Carcass

16 Breaker

17 Band

20 Sealant

21 Wider portion

30 Nozzle

31 Tip of nozzle

40 Non-contact displacement sensor

50 Rotary drive device

60 Twin screw kneading extruder

61 (61 a, 61 b, 61 c) Supply port

62 Material feeder

d, d₀, d₁, d₂ Distance between inner periphery of tire and tip of nozzle

1. A pneumatic tire, comprising a sealant layer located radially insidean innerliner, the sealant layer being formed by applying a sealant toan inner periphery of a tire from which mold release agents have beenremoved.
 2. The pneumatic tire according to claim 1, wherein the sealantlayer is formed by continuously and spirally applying a generallystring-shaped sealant to an inner periphery of a tire from which moldrelease agents have been removed, in a tire width direction from oneside to the other.
 3. The pneumatic tire according to claim 1, wherein asurface of the inner periphery of a tire is scraped.
 4. The pneumatictire according to claim 1, wherein the sealant is applied to an entirearea of the inner periphery of a tire from which mold release agentshave been removed.
 5. The pneumatic tire according to claim 4, wherein alength of the sealant layer in a tire width direction and a length inthe tire width direction of the area of the inner periphery of a tirefrom which mold release agents have been removed satisfy the followingformula:0 mm<(the length of the sealant layer in a tire width direction)−(thelength in the tire width direction of the area from which mold releaseagents have been removed)≦16.0 mm.
 6. The pneumatic tire according toclaim 1, wherein a length in a tire width direction of an area of thesealant layer formed by applying a sealant to an inner periphery of atire from which mold release agents have been removed and a length of abreaker of the tire in the tire width direction satisfy the followingformula:0 mm≦(the length in a tire width direction of an area of the sealantlayer formed by applying a sealant to an inner periphery of a tire fromwhich mold release agents have been removed)−(the length of a breaker inthe tire width direction)≦8.0 mm.
 7. The pneumatic tire according toclaim 2, wherein an attachment start portion of the sealant is locatedtire-widthwise inward from a tire-widthwise end of the sealant layer. 8.The pneumatic tire according to claim 7, wherein the sealant layer isformed by continuously applying a generally string-shaped sealant to aninner periphery of a tire from the attachment start portion toward thetire-widthwise end of the sealant layer, and then continuously andspirally applying a generally string-shaped sealant to the innerperiphery of a tire from the tire-widthwise end of the sealant layertoward the other tire-widthwise end of the sealant layer.
 9. Thepneumatic tire according to claim 8, wherein an application positionassumed when the sealant is applied from the attachment start portiontoward the tire-widthwise end of the sealant layer is moved in a tirewidth direction at a higher velocity than an application positionassumed when the sealant is applied from the tire-widthwise end of thesealant layer toward the other tire-widthwise end of the sealant layer.10. The pneumatic tire according to claim 1, wherein an attachment startportion of the sealant is located within an area of the inner peripheryof a tire from which mold release agents have been removed.
 11. Thepneumatic tire according to claim 1, wherein the sealant comprises arubber component including a butyl-based rubber, a liquid polymer, andan organic peroxide, and the sealant comprises 1 to 30 parts by mass ofan inorganic filler relative to 100 parts by mass of the rubbercomponent.
 12. The pneumatic tire according to claim 1, wherein thesealant layer has a thickness of 1.0 to 10.0 mm.
 13. The pneumatic tireaccording to claim 1, wherein the sealant layer has a width that is 85%to 115% of that of a breaker of the tire.
 14. The pneumatic tireaccording to claim 1, wherein the sealant layer is formed bysequentially preparing a sealant by mixing raw materials including acrosslinking agent using a continuous kneader, and sequentially applyingthe sealant to an inner periphery of a tire.
 15. The pneumatic tireaccording to claim 14, wherein the sealant discharged from an outlet ofthe continuous kneader has a temperature of 70° C. to 150° C.
 16. Thepneumatic tire according to claim 2, wherein a surface of the innerperiphery of a tire is scraped.
 17. The pneumatic tire according toclaim 2, wherein the sealant is applied to an entire area of the innerperiphery of a tire from which mold release agents have been removed.18. The pneumatic tire according to claim 3, wherein the sealant isapplied to an entire area of the inner periphery of a tire from whichmold release agents have been removed.
 19. The pneumatic tire accordingto claim 2, wherein a length in a tire width direction of an area of thesealant layer formed by applying a sealant to an inner periphery of atire from which mold release agents have been removed and a length of abreaker of the tire in the tire width direction satisfy the followingformula:0 mm≦(the length in a tire width direction of an area of the sealantlayer formed by applying a sealant to an inner periphery of a tire fromwhich mold release agents have been removed)−(the length of a breaker inthe tire width direction)≦8.0 mm.
 20. The pneumatic tire according toclaim 3, wherein a length in a tire width direction of an area of thesealant layer formed by applying a sealant to an inner periphery of atire from which mold release agents have been removed and a length of abreaker of the tire in the tire width direction satisfy the followingformula:0 mm≦(the length in a tire width direction of an area of the sealantlayer formed by applying a sealant to an inner periphery of a tire fromwhich mold release agents have been removed)−(the length of a breaker inthe tire width direction)≦8.0 mm.